1. Field of the Invention
The present invention relates to a process for producing a shaped and drawn aromatic imide polymer article. More particularly, the present invention relates to a shaped and drawn aromatic imide polymer article, for example, a film or filament, having enhanced physical properties, for example, an excellent heat resistance and an enhanced tensile strength and modulus of elasticity.
2. Description of the Related Art
It is known that an aromatic imide polymer is usable for producing a shaped and drawn article. For example, Japanese Examined Patent Publication (Kokoku) No. 57-41330 discloses a process for producing a heat-shrinkable aromatic imide polymer film. In this process, a solution of an aromatic imide polymer precursor, for example, an aromatic polyamic acid or aromatic polyamide acid, in an organic solvent is converted to a film by a spreading method, the resultant precursor film is heat-dried at a temperature of 200.degree. C. to 500.degree. C. to an extent such that the resultant dried film contains less than 10% by weight of a volatile substance and at least 50% by weight of the aromatic imide polymer precursor in the film is converted to the corresponding imide polymer, and the resultant dried membrane is then drawn in at least one direction at a draw ratio of 1.05 to 5.0 and at a temperature of 100.degree. C. to 500.degree. C., to provide an aromatic imide polymer film.
In this method, the dried film, which contains the non-imidized portion of the aromatic imide polymer precursor together with the completely imidized portion thereof, is drawn, and thus the drawing procedure is effected while the non-imidized portion of the aromatic imide polymer precursor is imidized. Accordingly, it is difficult to stably carry out the drawing procedure. Also, it is difficult or practically impossible to stably produce a shaped and drawn aromatic imide polymer article having a very high tensile strength and modulus of elasticity.